Pressure reducing air gun

ABSTRACT

An air gun designed to offer extra protection in the forms of an air screen barrier developed around a main discharged air stream to reduce the danger of chip fly back and air overload pressure relief means for reducing static nozzle pressure to a value less than any value as established by any regulatory agency for safety purposes.

United States Patent 1191 Gavin Dec. 25, 1973 PRESSURE REDUCING AIR GUN 3,599,876 8/1971 Kyburg 239/498 x [76] Inventor: Thomas M. Gavin, 35 Roseland Ter., Longmeadow, Mass. 01 106 Primary Examiner-M. Henson Wood, Jr. Assistant Examiner-Michael Y. Mar

[22] Flled' 1972 Attorney-Kenwood Ross et al. [21] Appl. No.: 309,065

[57] ABSTRACT [52] US. Cl. 239/291, 239/569 An air g designed to offer extra protection in the [51] Int. Cl B05b 1/28 f f b d I d d [58] Field of Search 239/291, 295, 525, F 9 i eve a mam dlscharged a1r stream to reduce the danger of ch1p fly back and an overload pressure rellef means UNITED STATES PATENTS safety purposw 2,783,092 2/1957 Gavin et a1. 239/291 3,318,534 5/l967 Stolteben 239/291 3 Claims, 3 Drawing Figures 4O 42 46 I2 1 i T 4'm" 8 +P|l||| PRESSURE REDUCING AIR GUN As known, compressed air is widely used as a power source in industry, a pressure usually in the area of 85 100 psi being furnished by a compressor to various air-powered instruments such as riveting guns, presses, jackhammers and like pneumatic tools. And as also known, workmen have used streams of compressed air for removing dust, metal chips and the like from work pieces, work benches and other areas.

When the workman wishes to dust, he manually opens the valve and aims the gun to direct a highvelocity, low-volume stream of air toward the object to be dusted. Lightweight particles of dust, metal chips and the like which are struck by the aim stream are accelerated thereby and fly off in various directions through the air.

Obviously, dusting by this means is a very unsafe practice and there have been many injuries attributed to flying particles being lodged in workmens eyes and in other parts of their bodies. Other injuries result when the orifice of a gun is, as a practical joke, pushed against a workman s body or into one of his body openings. The high-pressure stream of air will pass through the epidermis and into the blood stream, with the consequent air bubbles in the blood sometimes causing immediate death.

Safety engineers have long recognized the hazards of guns with the result that in some manufacturingplants their use is forbidden.

Recently adopted governmental safety regulations have related to the sensitive problem of insuring that air pressure in air guns for cleaning purposes does not exceed 30 psi static pressure.

The requirement to reduce the static nozzle pressure to less than 30 psi is understood to mean that the downstream pressure of the air at the nozzle or opening of a gun used for cleaning purposes, meaning nozzle pressure, must remain at a pressure level 30 psi for all static conditions. The requirements for dynamic flow are such that, in a case where dead ending occurs, a static pressure at the main orifice shall not exceed 30 psi. This requirement is necessary in order to prevent a back pressure buildup in case the nozzle is obstructed or dead ended.

Two acceptable methods for meeting the general requirement are already known and obvious.

In the first instance, assuming the primary feed line from the compressor to such as a pneumatic tool or other use (other than a cleaning use) to be at, say, 90 psi, a secondary line for the cleaning operation may be tapped into the primary feed line, which secondary line may be interrupted with an air pressure reducer where the inlet pressure is of course 90 psi but where the outlet pressure is a lesser value. The air in the secondary line, thus reduced with respect to pressure, can then be passaged to the air gun for use in the cleaning function.

In the second instance, again assuming the feed line to be at say 90 psi, the secondary line tapped thereinto can lead directly to the gun which incorporates its own pressure reducer, capable of reducing the air pressure to a desired lower value.

The invention hereof offers another approach responsive to the government regulation.

By this invention, the dangers of a blast gun with its wasteful over-kill are obviated. Rather the gun incorporates a safety feature whereby the nozzle pressure is limited to a maximum of 30 psi, or other desired value at normal air line pressure while yet retaining the necessary velocity for effective chip removal.

The invention combines means for facilitating the delivery of a jet of air at a predetermined pressure within a range of pressures in combination with means for projecting a conical barrier stream of air forwardly around the air jet to reduce the danger of fly-back by preventing chips and turnings or other blow-off debris dislodged by the air jet from flying back and striking the operator.

In the drawings:

FIG. 1 is a combined side elevational and longitudinal sectional view of the air gun of the invention;

FIG. 2 is an enlarged side elevational view of the nozzle of the invention; and

FIG. 3 is a view, in section, on line 2--2 of FIG. 2.

A gun body, generally represented by 10, has a grip or inlet end 12 and a nozzle or outlet end 14 angularly related thereto.

Grip end 12 is formed with a passage 16 leading thereinto from a threaded inlet 18, allowing connection with the flexible hose of a conventional compressed air line (not shown).

Passage 16 communicates at its inboard terminal with a circular valve well or cavity 20 in the gun body, which well is formed with an intermediate annular shoulder serving as a valve seat for a valve 22 having a usual resilient seat 24 and a lower stem 26 depending therefrom.

Valve 22 is reciprocable relative to the body so that, in closed position, as shown, the valve rests on the valve seat of the valve well to close off communication between the upper and lower regions of the valve well and in opened position, the valve is upwardly of the valve seat to allow communication between the upper and lower regions of the valve well.

A trigger 30 of conventional configuration is pivotally mounted on the body by means of a trigger pin 32 and the lower extremity of valve stem 26 extendable through a suitable opening in the gun body normally seats thereupon outboard of the trigger pin with a trigger spring 28 circumscribing the stem and a knurled manually-engageable adjusting nut 34 threadedly engaged with the lower extremity of the stem below the trigger spring.

As trigger 30 is operated upwardly, valve 22 is elevated upwardly of its seat to an open position thereabove. Adjusting nut 34 serves to limit upward movement of the valve and stem.

The upper wall of valve well 20 is threaded and a hex nut 42 having a depending threaded portion 40 is threadedly engaged therewith in the valve well closing function. A gasket 44 circumscribes threaded portion 40 to ensure a tight closure.

A valve spring 46 nestably seats in opposed spring seats in threaded portion 40 and valve 22 and urges the valve returnably onto its seat when the raised trigger is manually released.

Nozzle end 14 has a passage 50 leading thereinto from an outlet 52.

A nozzle, generally indicated by 60, comprises a tapered main body portion 62 positionable outside of the gun body and a shank or neck portion 64, which shank portion is positionable within the gun body, by being extended into passage 50 through outlet 52.

An annular shoulder 66 defines the rearward end and largest circumference of the main body portion, and

the shank portion is connected to the main body portion as by a tapered flared wall 68 complemental to the tapered mouth of outlet 52.

The nozzle is secured relative to the gun body by means of a transversely-extending staking pin 70 in manner such that an annular outlet generally indicated by 80 of any desired width or thickness and resultant from the judicious spacing of tapered wall 68 from the tapered mouth of outlet 52 allows a conical air stream to pass from the gun in the form of an umbrella of air around a main air stream discharged through a central passage 84 extending through the nozzle.

The outboard end of the nozzle has a nozzle tip 82 threadedly engaged therewith and air passageway 84 extends through the aligned nozzle and nozzle tip.

Circumferentially of shank portion 64, adjacent its upper terminal, an annular upper recess 72 is provided and the shank above the upper recess is formed with a plurality of peripherally-arranged circumferentiallydisposed longitudinally-extending flutes 74 communicating with the recess. Below the upper recess, the shank is provided with a plurality of peripherallyarranged circumferentially-disposed longitudinallyextending flutes 76 likewise communicating with upper recess 72 thereabove and with another annular lower recess 78 adjacent tapered wall 68.

An overload relief means or automatic safeguard is in the form of a spring means 86 disposed around the neck of the shank defined by the bottom wall of the recess and a plurality of radially-extending openings 88 extend through the shank in a circumferential row about the neck and communicating with central passage 84.

The combined area of openings 88 is capable of bleeding off sufficient air from within passageway 84 to maintain the pressure therewithin at the desired safe level.

Spring means 86 which may be formed of a strip of metal or rubber is of a width equal to the width of recess 72 and of a length greater than the circumference of the recess as may be seen in FIG. 3.

The strip may be placed in position by inserting one end in the bottom of the recess and sliding the strip around the recess circumference until it passes completely around the recess and ultimately to commence a second convolution about the neck in overlapping relation.

The fit between the edges of the strip and the walls of the recess is sufficiently loose to enable the strip to be fitted into the recess but sufficiently tight to prevent an appreciable loss of pressure or air from within passageway 88 when the strip is in its sealing position with respect to the holes. The overlapping of the ends of the strip when in the final position will result in the strips forming a complete cylinder about the area of the neck containing the holes and will effectively prevent the loss of any appreciable amount of pressurized gas from within the gun.

In the event that the pressure within the gun should rise above the maximum safe level, the internal pressure on the'strip will cause it to buckle and curve in a direction normal to the direction of curvature which it has assumed as a result of being wrapped around the shank. This will cause the edges of the strip to move towards each other due to distortion of the strip and, ultimately, the strip will be sprung away from the recess walls thereby permitting the holes to spill the contents of the gun and thereby reduce the pressure to a safe level. The advantages of the pressure relief system constructed in accordance with the present invention are several and of considerable importance.

Advantage resides in the fact that the curvature of the strip which results from its being wrapped around the shank greatly increases its resistance to bending in a direction normal to the direction of primary curvature and, as a result, a strip of sheet metal or other material may be used which is considerably thinner and lighter than might otherwise be the case. The primary curvature of the strip imparts considerable rigidity to the entire assembly which enables a relatively light assembly to be used even when high pressures are contemplated.

Passage 50 in nozzle end 14 communicates with well 20 below the annular seat on the well by means of a secondary passage 98.

Normally air entering the gun through the inlet passes through passage 16 and, when the valve is raised from its seat past the valve in the well and into and through passage 98 to and through passage 50 and outwardly of passage 84 in the nozzle and nozzle tip to atmosphere with a minor quanta of the air passing through flutes 74, upper recess 72, flutes 76, lower recess 78 and passage to atmosphere in the umbrella like barrier around the main air stream.

If and when the dead ending or obstructing of the nozzle occurs so that there is a back pressure buildup within passage 50, the spring 86 is forced to rise up from its seat upon the recess wall by the force of air through passages 88 and the air thereby escapes into the recess and thence outwardly through flutes 76 and through lower recess 78 to passage 80 to atmosphere.

Release of the obstruction or termination of the dead ending allows the spring to return to its normal seated position.

lclaim:

1. In an air gun having an air inlet and an air outlet and valve means therebetween:

the improvement in means for the discharge from the outlet of a mainstream air jet and an umbrella jet of air circumscribed therearound with an increase in the discharge in the umbrella jet of air during a condition of overload relief comprising:

an elongated nozzle having an elongated upper shank portion fixed in the gun with an outer surface contiguous with the inner surface of the gun and a lower main body portion extending downwardly therefrom and outwardly of the outlet,

said nozzle having a central bore longitudinally thereof for the discharge of air in the form of a mainstream jet at the outer end thereof,

the shank having an annular recess adjacent the upper end thereof and a set of peripherally arranged longitudinally extending flutes on opposite sides of the recess disposed relative to the longitudinal shank axis,

a spring means normally seated in the recess of the shank,

a plurality of radially arranged passageways extending through the shank between the seat of the spring means and the central bore of the nozzle,

the spring means lifting from its seat in the recess upon pressure build up within the central bore of the nozzle through any dead ending of the nozzle.

2. An air gun comprising in combination:

a body having an air inlet and outlet and a well provided with a valve seat therebetween,

the body having air passageways from the inlet to the well above the seat and from the well below the seat to the jet means,

a valve engageable with the seat having a stem extending through the body,

spring means urging the valve towards the seat,

a trigger operable to act on the stem to elevate the stem and valve from the seat,

internal stop means to limit movement of the valve from the seat in the form of a stop member adjustable in the well and engageable by the valve as it is elevated by the trigger means for the discharge from the outlet of a mainstream air jet and an embrella jet of air circumscribed therearound with an increase in the discharge in the umbrella jet of air during a condition of overload relief and including:

an elongated nozzle having an elongated upper shank portion fixed in the gun with an outer surface contiguous with the inner surface of the gun and a lower main body portion extending downwardly therefrom and outwardly of the outlet,

said nozzle having a central bore longitudinally thereof for the discharge of air in the form of a mainstream jet at the outer end thereof,

the shank having an annular recess adjacent the upper end thereof and a set of peripherally arranged longitudinally extending flutes on opposite sides of the recess disposed relative to the longitudinal shank axis,

a spring means normally seated in the recess of the shank,

a plurality of radially arranged passageways extending through the shank between the seat of the spring means and the central bore of the nozzle,

the spring means lifting from its seat in the recess upon pressure build up within the central bore of the nozzle through any dead ending of the nozzle, 3. In an air gun having an air inlet and an air outlet and valve means therebetween:

the improvement in means for the discharge from the outlet of a mainstream air jet and an umbrella jet of air circumscribed therearound with an increase in the discharge in the umbrella jet of air during a condition of overload relief comprising:

an elongated nozzle having an elongated upper shank portion fixed in the gun with an outer surface contiguous with the inner surface of the gun and a lower main body portion extending downwardly therefrom and outwardly of the outlet,

said nozzle having a central bore longitudinally thereof for the discharge of air in the form of a mainstream jet at the outer end thereof,

the shank having an annular recess adjacent the upper end thereof defining a pair of collars extending radially outwardly of the external surface of the recess and spaced axially of one another and a set of peripherally arranged longitudinally extending flutes in the collars on opposite sides of the recess disposed relative to the longitudinal shank axis,

a plurality of radially arranged passageways extending through the shank between the seat of the spring means and the central bore of the nozzle,

the spring means lifting from its seat in the recess upon pressure build up within the central bore of the nozzle through any dead ending of the nozzle,

a series of holes in the shank between the two collars,

a pressure relief device in the form of a strip of sheet material ofa width equal to the separation between the two collars and of a length greater than the circumference of the recess,

surrounding the recess between the collars with its ends in overlapping relationship to seal the holes in the shank. 

1. In an air gun having an air inlet and an air outlet and valve means therebetween: the improvement in means for the discharge from the outlet of a mainstream air jet and an umbrella jet of air circumscribed therearound with an increase in the discharge in the umbrella jet of air during a condition of overload relief comprising: an elongated nozzle having an elongated upper shank portion fixed in the gun with an outer surface contiguous with the inner surface of the gun and a lower main body portion extending downwardly therefrom and outwardly of the outlet, said nozzle having a central bore longitudinally thereof for the discharge of air in the form of a mainstream jet at the outer end thereof, the shank having an annular recess adjacent the upper end thereof and a set of peripherally arranged longitudinally extending flutes on opposite sides of the recess disposed relative to the longitudinal shank axis, a spring means normally seated in the recess of the shank, a plurality of radially arranged passageways extending through the shank between the seat of the spring means and the central bore of the nozzle, the spring means lifting from its seat in the recess upon pressure build up within the central bore of the nozzle through any dead ending of the nozzle.
 2. An air gun comprising in combination: a body having an air inlet and outlet and a well provided with a valve seat therebetween, the body having air passageways from the inlet to the well above the seat and from the well below the seat to the jet means, a valve engageable with the seat having a stem extending through the body, spring means urging the valve towards the seat, a trigger operable to act on the stem to elevate the stem and valve from the seat, internal stop means to limit movement of the valve from the seat in the form of a stop member adjustable in the well and engageable by the valve as it is elevated by the trigger means for the discharge from the outlet of a mainstream air jet and an embrella jet of air circumscribed therearound with an increase in the discharge in the umbrella jet of air during a condition of overload relief and including: an elongated nozzle having an elongated upper shank portion fixed in the gun with an outer surface contiguous with the inner surface of the gun and a lower main body portion extending downwardly therefrom and outwardly of the outlet, said nozzle having a central bore longitudinally thereof for the discharge of air in the form of a mainstream jet at the outer end thereof, the shank having an annular recess adjacent the upper end thereof and a set of peripherally arranged longitudinally extending flutes on opposite sides of the recess disposed relative to the longitudinal shank axis, a spring means normally seated in the recess of the shank, a plurality of radially arranged passageways extending through the shank between the seat of the spring means and the central bore of the nozzle, the spring means lifting from its seat in the recess upon pressure build up within the central bore of the nozzle through any dead ending of the nozzle.
 3. In an air gun having an air inlet and an air outlet and valve means therebetween: the improvement in means for the discharge from the outlet of a mainstream air jet and an umbrella jet of air circumscribed therearound with an increase in the discharge in the umbrella jet of air during a condition of overload relief comprising: an elongated nozzle having an elongated upper shank portion fixed in the gun with an outer surface contiguous with the inner surface of the gun and a lower main body portion extending downwardly therefrom and outwardly of the outlet, said nozzle having a central bore longitudinally thereof for the discharge of air in the form of a mainstream jet at the outer end thereof, the shank having an annular recess adjacent the upper end thereof defining a pair of collars extending radially outwardly of the external surface of the recess and spaced axially of one another and a set of peripherally arranged longitudinally extending flutes in the collars on opposite sides of the recess disposed relative to the longitudinal shank axis, a plurality of radially arranged passageways extending through the shank between the seat of the spring means and the central bore of the nozzle, the spring means lifting from its seat in the recess upon pressure build up within the central bore of the nozzle through any dead ending of the nozzle, a series of holes in the shank between the two collars, a pressure relief device in the form of a strip of sheet material of a width equal to the separation between the two collars and of a length greater than the circumference of the recess, surrounding the recess between the collars with its ends in overlapping relationship to seal the holes in the shank. 